merge bitcoin#21327: ignore transactions while in IBD

`p2p_ibd_txrelay.py` was introduced in bitcoin#19423 but not backported
as Dash doesn't have feefilter capabilities but this backport has the
test check for additional cases which are within Dash's capabilities, so
the test has been committed in with the feefilter portions minimally
stripped out

src/net_processing.cpp

@@ -4053,6 +4053,11 @@ void PeerManagerImpl::ProcessMessage(
     }
 
     if (msg_type == NetMsgType::TX || msg_type == NetMsgType::DSTX) {
+        // Stop processing the transaction early if we are still in IBD since we don't
+        // have enough information to validate it yet. Sending unsolicited transactions
+        // is not considered a protocol violation, so don't punish the peer.
+        if (m_chainman.ActiveChainstate().IsInitialBlockDownload()) return;
+
         CTransactionRef ptx;
         CCoinJoinBroadcastTx dstx;
         int nInvType = MSG_TX;

test/functional/p2p_ibd_txrelay.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+# Copyright (c) 2020 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test transaction relay behavior during IBD:
+- Don't request transactions
+- Ignore all transaction messages
+"""
+
+from decimal import Decimal
+import time
+
+from test_framework.messages import (
+    CInv,
+    COIN,
+    CTransaction,
+    from_hex,
+    msg_inv,
+    msg_tx,
+    MSG_TX,
+)
+from test_framework.p2p import (
+    NONPREF_PEER_TX_DELAY,
+    P2PDataStore,
+    P2PInterface,
+    p2p_lock
+)
+from test_framework.test_framework import BitcoinTestFramework
+
+NORMAL_FEE_FILTER = Decimal(100) / COIN
+
+class P2PIBDTxRelayTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.disable_mocktime = True
+        self.num_nodes = 2
+        self.extra_args = [
+            ["-minrelaytxfee={}".format(NORMAL_FEE_FILTER)],
+            ["-minrelaytxfee={}".format(NORMAL_FEE_FILTER)],
+        ]
+
+    def run_test(self):
+        self.log.info("Check that nodes don't send getdatas for transactions while still in IBD")
+        peer_inver = self.nodes[0].add_p2p_connection(P2PDataStore())
+        txid = 0xdeadbeef
+        peer_inver.send_and_ping(msg_inv([CInv(t=MSG_TX, h=txid)]))
+        # The node should not send a getdata, but if it did, it would first delay 2 seconds
+        self.nodes[0].setmocktime(int(time.time() + NONPREF_PEER_TX_DELAY))
+        peer_inver.sync_send_with_ping()
+        with p2p_lock:
+            assert txid not in peer_inver.getdata_requests
+        self.nodes[0].disconnect_p2ps()
+
+        self.log.info("Check that nodes don't process unsolicited transactions while still in IBD")
+        # A transaction hex pulled from tx_valid.json. There are no valid transactions since no UTXOs
+        # exist yet, but it should be a well-formed transaction.
+        rawhex = "0100000001b14bdcbc3e01bdaad36cc08e81e69c82e1060bc14e518db2b49aa43ad90ba260000000004a01ff473" + \
+            "04402203f16c6f40162ab686621ef3000b04e75418a0c0cb2d8aebeac894ae360ac1e780220ddc15ecdfc3507ac48e168" + \
+            "1a33eb60996631bf6bf5bc0a0682c4db743ce7ca2b01ffffffff0140420f00000000001976a914660d4ef3a743e3e696a" + \
+            "d990364e555c271ad504b88ac00000000"
+        assert self.nodes[1].decoderawtransaction(rawhex) # returns a dict, should not throw
+        tx = from_hex(CTransaction(), rawhex)
+        peer_txer = self.nodes[0].add_p2p_connection(P2PInterface())
+        with self.nodes[0].assert_debug_log(expected_msgs=["received: tx"], unexpected_msgs=["was not accepted"]):
+            peer_txer.send_and_ping(msg_tx(tx))
+        self.nodes[0].disconnect_p2ps()
+
+        # Come out of IBD by generating a block
+        self.nodes[0].generate(1)
+        self.sync_all()
+
+        self.log.info("Check that nodes process the same transaction, even when unsolicited, when no longer in IBD")
+        peer_txer = self.nodes[0].add_p2p_connection(P2PInterface())
+        with self.nodes[0].assert_debug_log(expected_msgs=["was not accepted"]):
+            peer_txer.send_and_ping(msg_tx(tx))
+
+if __name__ == '__main__':
+    P2PIBDTxRelayTest().main()

test/functional/test_framework/p2p.py

@@ -99,6 +99,8 @@ P2P_SERVICES = NODE_NETWORK | NODE_HEADERS_COMPRESSED
 P2P_SUBVERSION = "/python-p2p-tester:0.0.3%s/"
 # Value for relay that this test framework sends in its `version` message
 P2P_VERSION_RELAY = 1
+# Delay after receiving a tx inv before requesting transactions from non-preferred peers, in seconds
+NONPREF_PEER_TX_DELAY = 2
 
 MESSAGEMAP = {
     b"addr": msg_addr,

test/functional/test_runner.py

@@ -306,6 +306,7 @@ BASE_SCRIPTS = [
     'rpc_estimatefee.py',
     'p2p_unrequested_blocks.py', # NOTE: needs dash_hash to pass
     'feature_shutdown.py',
+    'p2p_ibd_txrelay.py',
     'rpc_coinjoin.py',
     'rpc_masternode.py',
     'rpc_mnauth.py',